Bedrock localization with deep imaging up to 500 ft/152m

04/04/2023
Geophyscal Engineering Monitoring

REQUEST

Map bedrock depth confirmation after drilling campaign.

Bedrock depth was not found by drilling as probably to deep.

Infrastructure monitoring

SOLUTIONS

To secure what will be done, a deep imaging results up to 500 ft/152 m has been realized.

  • Deployments of ultra dense accelerometers array
  • Specific processing of low frequencies

Blue Line 1 : 300 ft/91 m lenght ,  100 sensors, 3 ft/90 cm spacing

Green line 2 : 100 ft/30 m lenght, 100 sensors,  1 ft/30 cm spacing

GEM S-scan

CONCLUSION

  1. Results show shear wave velocity versus depth up to 200 ft/61 m are consistent between Lines 1 and 2
  2. The results show that there exists deep silt deposit, relatively uniform up to 200 ft/61 m 
  3. Finally the bedrock is deeper than expected and not accessible by drilling or too expensive by this method.
  4. Bedrock position is 220ft/67 m deep.

 

SHM